1. Field of the Invention
This invention relates to a molding process for various ceramic products, particularly to a pressure slipcast molding of ceramic slurry, and a mold used therefore.
2. Description of the Prior Art
In a pressure slipcast molding process, a mixture consisting of powder and liquid (hereinafter xe2x80x9cslurryxe2x80x9d) is pressurized to discharge the liquid therefrom. In this process, the higher the pressure is, the more densely the powder is compacted. Thus, the resulting molded article has a high geometric stability and the liquid discharge and from the slurry can be made in reduced time. In the conventional pressure slipcast molding, porous molds made from gypsum or plastics have been used for the liquid discharge, (e.g. Japanese Patent Publication No. 2-42321, Japanese Patent Laid-Open Nos. 60-70701, 63-3906 and 61-297103).
However, since these porous materials constituting the conventional molds do not have a sufficient strength, the molding pressure is, at most only 10 kg/cm2 when a gypsum mold is used and about 50 kg/cm2 when a plastics mold is used. If the molding pressure exceeding this upper limit is applied to the porous mold, such high pressure may bring about the breakage of the molds. Thus, there is limitation in improving the density of ceramic molded articles and it becomes impossible to mold in a short time, depending on the shape or the size. In the method of molding ferrite slurry and so on, a filter cloth 9 and a filter paper 10 are, as shown in FIG. 3, set at the frontal face of a metallic mold 3, which has holes of 1-3 mm inside diameter for dehydration. And only liquid (water) is discharged from the holes of the mold through the filter.
In the method as shown in FIG. 3, since the liquid discharge part consists of the filter cloth 9, filter paper 10 and mold 3 having the holes 4 for dehydration, a high molding pressure can be applied. However in this case, when pressure is applied, the powder in the slurry enters the holes for dehydration pressing on the filter paper or filter cloth and then it becomes protrusions 11 are formed on the surface of the molded product, corresponding to the holes as shown in FIG. 4. Therefore, an after-treatment is necessary to remove the protrusion from the molded product, thereby resulting in a high production cost.
With the above in view, the present invention was made to overcome the above and other problems encountered in the prior art.
It is an object of the present invention to provide a process for slipcast molding of ceramics, with a smooth surface in which a higher pressure is applied as compared with a conventional process.
Another object of the present invention is to provide molds used for carrying out the above-mentioned molding process.
The basic idea of this invention is to enable the application of high pressure by using a mold made of a high-strength porous metal or ceramic material in a pressure slipcast molding process of a ceramic slurry.
To the above and other ends, the present invention provides a process for molding a ceramic slurry, in which a mold made wholly or partially of a porous metal or a porous ceramic is used.
The present invention also provides a mold made wholly or partially of a porous metal or a porous ceramic, for the purpose of molding ceramic slurry.